Predation Flashcards
What effect does predation have on sp 1 vs sp 2?
Sp1- Negative
Sp2- Positive
Whats predation?
-Interaction between consumers (predators) and resources (victims, prey)
What increases predator population growth?
Reduction in prey population
What does the Lotka-Volterra predator-prey model assume? Is it realistic? What effect of predators is it trying to see?
- Specialist predator on single prey (narrow range of conditions)
- Victim pop is limited by predators
- Predator/prey regulate one another’s populations
- No; As soon as predator feeds on prey using energy to go into reproduction
- How much predator population will decrease per capita growth rate of prey
What does alpha stand for?
Every time predator captures a victim- how many times will they be successful?
-Capture efficiency
How does the equilibrium for V depends on P?
Only few predators wont be able to control prey population- prey pop increase and vice versa
What does predator growth depend on?
Prey abundance
Whats neutral stability?
Will cycle with different amplitude if perturbed (unsettled)
1 way to increase realism of Lotka-Volterra model? What does the victim isocline produce? Why more stable?
- Victim carrying capacity
- Density Dependence
- Can run out of resources
- Damped oscillations
- Victim pop is regulated by another factor besides predator
Whats a basic functional response?
- Rate of victim capture by predator as a function of victim abundance
- Type I
- Increases realism
Explain Type II functional response. What does it arise from?
-At high prey
predators get full
time needed to consume victims (handling time)
- Handling time- Time needed to “handle” prey reduces overall consumption rate
Explain Type III functional response.
-At high prey: predators get full
time needed to consume victims (handling time)
-At low prey: Poor search image, Prey refugia (hiding places), and Switch to other prey
What is type I fractional response?
Linear horizontal line
What is type II fractional response?
- Fractional consumption rate decreases with population increase
- Predator is having smaller impact on victims pop growth
- More realistic model for how quick predators can feed upon victims.
- More victims- predators consume less share of pop; less effective in regulating size of victims.
What is type III fractional response?
Fraction consumed increase initially- but will plateau- victims go up more but smaller impact
What does the victim isocline with a type II functional response produce?
- Increasing unstable oscillations
- Not stable because predator is less effective at regulating victim pop
Whats the Rosenzweig-Macarthur model?
- Combines prey density-dependence with Type II predator functional response
- Simplest “realistic” model of predator-prey systems
Rosenzweig-Macarthur model victims isocline. What does the stability depend on?
- Parabola
- Predator isocline
Whats the Paradox of Enrichment?
- As CC increases, victim pop destabilizes because predator is more responsible for its suppression
- Lower CC- stable
- Increase CC- limit cycles
- very high cc- intersect predator isoline; unstable pop; 1 or 2 species will go extinct
Why might predator isocline not be vertical?
Predator interference
→ must defend territory or fight other predators
Predator density-dependence
→ regulated by other factors when excess victims
Alternative prey sources
→ switch to other prey when few victims
Victims have density-dependent effects
→ stable ratio of predators to victims
3 considerations for each potential item in the optimal foraging theory.
- Energy (Ei) = net calories obtained
- Encounter rate (λi) = # found per unit search time
- Handling time (hi) = time needed to consume
Diet preference is based on?
The profitability of each item:
-Profitability = Ei/hi
(rate of energy gain once prey has been located)
- The most profitable items should always be included in diet
- Less profitable items may or may not be included
What is energy intake?
E/T
Should profitability or energy intake be more?
Profitability
